The present invention relates generally to underwater structures. More specifically, the present invention pertains to artificial reef structures. The present invention is particularly, though not exclusively, useful as an artificial, non-permanent reef structure that can be placed underwater in tropical marine environments to promote the settlement and growth of benthic invertebrates, to provide shelter and protection for schools of small reef fish, and ultimately, to promote the re-growth of damaged coral and the growth of new coral.
Coral reefs are extremely complex marine ecosystems which are home to numerous aquatic species. Coral reefs are thought by many scientists to be the most biologically diverse, species-rich and productive ecosystems on the earth. Coral reefs occupy approximately two-tenths of a percent (0.2%) of the world""s ocean surfaces. However, it is estimated that coral reefs are home to nearly a million marine species, including a quarter of all fish species.
Corals are divided into two types: hard corals and soft corals. Hard corals, such as staghorn, elkhorn, and pillar corals, are stationary on the ocean floor and have rigid exoskeletons, or corallites, that protect the soft delicate bodies within their interior. Soft corals, or gorgonians, such as sea fans, sea whips, and sea rods, are also stationary on the ocean floor, but they lack an exoskeleton. The soft corals sway back and forth under the influence of the currents.
Coral reefs provide several important benefits to the world""s population. These benefits include tourism, private and commercial fishing, mainland and island protection, medicines, and ecological indications. Many people travel to coral reefs to snorkel, scuba-dive, and fish. For example, many island countries in the Pacific and Indian Oceans and in the Caribbean Sea derive a substantial portion or their income from the tourism attracted by the nearby coral reefs.
As previously mentioned, numerous types of fish find shelter in coral reefs and use them for spawning, feeding and nursing. Therefore, substantial income and employment may also be derived from commercial fisheries operating near coral reefs. Moreover, in poorer countries, many of the inhabitants reside within the coastal zones of developing regions and rely directly on fish caught at the nearby coral reefs for their necessary protein.
Coral reefs provide protection from coastal damage from intense wave action, such as coastal erosion and flooding. Older reefs have facilitated the formation of lagoons and calm shorelines where seagrass beds and mangrove trees flourish to provide shelter and habitat for numerous species at the coastal/aquatic interface.
Coral reefs are also a source of many important pharmaceutical breakthroughs. It is estimated that nearly one-half (xc2xd) of the potential pharmaceuticals presently being explored are from the oceansxe2x80x94many of which are found near coral reefs.
Finally, because of their susceptibility to minor temperature variations, coral reefs may provide indication of ecological changes much quicker than other ecosystems. For example, coral reefs may be among the first ecosystems to show signs of ecological stress from global warming and as such, coral reefs are very important ecologic indicators.
Unfortunately, many of the earth""s coral reefs are in danger of being severely injured or destroyed by human activity. Water pollution, global warming and direct physical contact from boat anchors, divers, etc., are among many of the causes of this deterioration. Moreover, the spread of non-sustainable fishing methods, such as dynamite fishing, have caused a rapid decline in the live coral cover on many of the world""s coral reefs.
As a result, many large reef tracts have been reduced to little more than vast fields of coral rubble. Because of the lack of a suitable habitat, reef fish, particularly the juveniles and the small herbivorous species, will quickly abandon a demolished reef. Young hard corals struggling for a foothold on the ocean floor may be easily smothered by carpets of algae, aggressive soft corals, and shifting reef sediment. Furthermore, without the successful recruitment of hard corals or fish to the coral reef, collapse of the ecosystem rapidly ensues. Under these circumstances, many decades are required to completely re-establish a highly diverse hard coral cover and propagate normal reef fish populations.
Hard corals may reproduce sexually or asexually. Sexual reproduction of coral involves spawning, fertilization and the production of planula larvae, some of which may live in plankton for up to one hundred (100) days. Asexual reproduction may include the budding of polyps from a parent colony, polyp bailout, or fragmentation. Polyp bailout occurs when a polyp abandons a corallite and re-establishes itself on a new substratum. Fragmentation is common with branching forms of coral and is a process by which new colonies may be initiated when a patent colony is broken up during a storm.
The growth of hard coral depends on its structure. Branching forms of hard coral, such as staghorn or Acropora, which grow linearly, grow at a rate between one hundred and two hundred millimeters per year (100-200 mm/yr). Massive colonies with dense skeletons, however, grow at a rate between six and twelve millimeters per year (6-12 mm/yr), but these colonies may live for centuries.
A thriving hard coral reef depends on the presence of mutually dependent organisms and the maintenance of the microhabitats that they require. One fundamental relationship for a thriving hard coral reef is the relationship between the coral and the small herbivorous reef fish. Overlapping and interlocking coral branches and coral plates create a complex, three-dimensional habitat having a multitude of intersticial spaces suitable for housing large populations of small reef fish. The different small, herbivorous fish species keep the corals free of rapidly growing algae that would otherwise quickly overwhelm and kill the corals.
The intersticial spaces created by the coral branches and plates also provide shelter for juvenile members of larger reef fish species and protect them from predators during their early growth years. Without the protection afforded by hard corals, populations of economically important reef fish would quickly decline.
Another fundamental relationship for a thriving hard coral is that which exists between established hard coral colonies and planktonic coral larvae in the water column seeking an appropriate place to settle and grow. On a healthy coral reef, lush hard coral growth stabilizes reef sediments by depositing a thick accumulation of broken coral branches and plates upon which the living corals grow. The upper part of this accumulation forms an open framework characterized by abundant shaded surfaces which are elevated above the level of shifting sediments.
Coral larvae prefer to settle in this microhabitat, and they tend to seek out the shaded undersides of the coral framework where they are protected from algae, grazing invertebrates and accumulating sediments. On a coral reef that has suffered extensive physical damage, this microhabitat is eliminated, and the recruitment of hard corals to the reef slows because coral larvae have great difficulty establishing in open, unprotected areas of sand, loose rubble, or rubble covered with carpets of algae and aggressive soft corals. This is the principal reason for the long recovery time of damaged coral reefs.
Artificial reefs have been explored as a means of speeding the recovery of damaged coral reefs. For example, U.S. Pat. No. 5,639,657, which issued in 1997 to Saiki et al. for an invention entitled xe2x80x9cProcess For Formation Of Artificial Seaweed Bedxe2x80x9d (the xe2x80x9c""657 patentxe2x80x9d) discloses an artificial reef system which is coated with a porous glassy material.
This glassy material contains silicon, ferrous iron, phosphorus, manganese, sodium and/or potassium. The glassy material will slowly dissolve in seawater releasing the component minerals. The dissolution of the glassy material depends on the porosity of the glassy material and the composition of the mineral components. The ""657 patent discloses a structure which is coated with the glassy material and submerged to form an artificial reef. Over time the glassy material will dissolve, and when the glassy material is fully dissolved the underlying structure will remain intact.
U.S. Pat. No. 5,564,369, which issued in 1996 to Barber et al. for an invention entitled xe2x80x9cReef Ballxe2x80x9d (the xe2x80x9c""369 patentxe2x80x9d), discloses a hollow, spherical reef module made from concrete. The outer wall of the reef module disclosed by the ""369 patent includes a plurality of different sized and different shaped holes leading to the interior space. The modules may be cast on shore around an inflatable bladder, dragged to the desired location, and submerged to the ocean floor by deflating the bladder.
U.S. Pat. Nos. 4,913,094, and 5,113,792, which issued in 1990 and 1992 to Jones et al. for inventions entitled xe2x80x9cArtificial Reef Systemxe2x80x9d (the xe2x80x9c""094 patentxe2x80x9d) and xe2x80x9cArtificial Reef Modulexe2x80x9d (the xe2x80x9c""792 patentxe2x80x9d), discloses a rectangular column composed of corrugated sheets which may be oriented horizontally or vertically.
The ""094 patent and the ""792 patent each include a heavy base which is attached to the column. This base is designed to hold the column on the ocean floor. Additionally, the ""094 patent and the ""792 patent are designed to remain intact. It is expected that over time microbial attachment, biofouling, and sedimentation will become completely sufficient to hide either the ""094 patent or the ""792 patent from view. This will create the appearance of a natural reef system.
U.S. Pat. No. 5,215,406, which issued in 1993 to Hudson for an invention entitled xe2x80x9cArtificial Ocean Reef Module And Method of Module Constructionxe2x80x9d (the xe2x80x9c""406 patentxe2x80x9d), discloses a heavy dome-like structure with man-made irregularities similar to naturally occurring reefs. The device of the ""406 patent is designed to last indefinitely. U.S. Pat. No. 3,898,958, which issued in 1975 to Pranis, Jr. for an invention entitled xe2x80x9cOpen Water Fish Farming Apparatusxe2x80x9d (the xe2x80x9c""958 patentxe2x80x9d), discloses a lattice composed of individual cubes. The framework of the cubes includes different sized openings to facilitate the sheltering of a variety of fish. The lattice is designed to be assembled on shore and then transported by boat to a location where it is submerged. The lattice is easily expandable and designed to last indefinitely.
Each of the above-mentioned artificial reefs is a permanent underwater structure designed to attract fish. There are also numerous other types of artificial reefs made from discarded pollutants such as tires, concrete blocks, wrecked cars, and sunken ships also designed to attract fish and aid in the remediation of damaged reefs. However, there is a growing consensus that these artificial reefs are generally ineffective.
It is widely held that artificial reef structures like the ones discussed above are poorly suited for the remediation of damage coral reefs, particularly in developing countries. In these regions, where vast areas of coral reefs have been severely damaged, there is an acute need to replenish reef fisheries in the face of sustained, intense fishing pressure. Moreover, there is a growing demand on the part of ecotourism operators and conservation agencies for the remediation of coral reefs to pristine condition.
Because of their cost and difficult installation, conventional artificial reefs typically end up covering such a small area of the reef that they fail to make a significant impact on the reproduction rates of hard corals and reef fish. Furthermore, conventional artificial reefs, such as the xe2x80x9cReef Ballxe2x80x9d disclosed by the ""369 patent, tend to attract and shelter adult fish, allowing important brood stocks to be easily fished out. They also fail to provide the complex, fine-scale habitat needed by juvenile fish or small herbivorous fish. Each of these artificial reefs is made from materials, such as metals, plastics and concrete, which are often chemically inappropriate for the settlement of delicate coral larvae. Additionally, these artificial reef designs often fail to account for and provide for the preferred microhabitats of settling coral larvae, such as the shaded undersides of coral plates. Finally, these artificial reefs are typically unsightly permanent structures, and due to their durability, these reefs preclude the opportunity for the natural coral reef to return to its original, pristine condition.
For the forgoing reasons, these conventional artificial reefs have not been widely accepted as means for repairing damaged coral reef ecosystems. Many coral reef ecologists and ecotourism operators regard these artificial reefs as a form of unattractive marine pollution with little remediation benefit and low potential for increasing ecotourism or fisheries"" revenues.
In light of the problems associated with the above discussed artificial reef structures, there is a need for a device made from nonpollutants which closely approximates the natural underwater habitat provided by thriving coral reefs. Moreover, there is a need for a non-permanent device which will degrade over a period of ten to twenty years (a typical minimum time span for coral reef establishment on denuded substrate), such that lasting signs of human intervention are minimized in the re-established ecosystem.
Accordingly, it is an object of the present invention to provide an artificial reef module for coral reef remediation that will closely approximate a natural coral reef habitat in order to attract the proper marine life to facilitate the re-growth of damaged coral and to facilitate the growth of new coral. It is another object of the present invention to provide an artificial reef module for coral reef remediation made from nonpolluting materials that will degrade over time to minimize evidence of human intervention.
It is another object of the present invention to provide an artificial reef module for coral reef remediation which, through the process of degradation, will approximate natural fragmentation of branching types of coral to aid in the dissemination of young corals and facilitate the reproduction of the coral. It is another object of the present invention to provide an artificial reef module for coral reef remediation that may be constructed from mass produced, prefabricated components to facilitate the deployment of the artificial reef modules in large numbers at low cost.
It is another object of the present invention to provide an artificial reef module for coral reef remediation that may be easily deployed freestanding or anchored and creates a useful habitat regardless of orientation on the ocean floor. It is another object of the present invention to provide an artificial reef module for coral reef remediation that may be easily modified or customized for a particular requirement or need by making simple variations in the dimensions or geometry of the module. It is yet another object of the present invention to provide an artificial reef module for coral reef remediation which, when deployed in plurality, creates an artificial reef structure with a natural, organic underwater appearance that is visually appealing to swimmers, snorkelers, and SCUBA divers.
The artificial reef module for coral reef remediation of the present invention includes a central body having an upper settling plate with an upper and lower surface, a middle settling plate with an upper and lower surface, and a lower settling plate with an upper and lower surface. Extending from the central body is a plurality of primary tines.
The primary tines include supporting tines, stabilizing tines, and space filling tines. Each primary tine includes a tip and a base and extending from each primary tine is a plurality of secondary tines. The branching of the tines closely replicates the appearance of natural branching coral.
The supporting tines and the stabilizing tines extend at an angle from the upper surface of the upper settling plate and the lower surface of the lower settling plate. The space filling tines extend radially outward from the middle settling plate. A plurality of vertical ribs provide support for the settling plates and the primary tines. The artificial reef module for coral reef remediation is symmetrical about the horizontal center line and the vertical center line.
The supporting tines and the stabilizing tines are oriented such that the tips of these tines are approximately the same vertical distance from the upper and lower settling plates. This allows the artificial reef module for coral reef remediation to rest stably on the ocean floor or seabed.
The artificial reef module for coral reef remediation may be constructed from six identical artificial reef module subcomponents. Each subcomponent may include five primary tines, a plurality of secondary tines, one vertical rib, and a one-sixth pie-shaped piece of each settling plate. In this configuration, the primary tines and the secondary tines would be vertically aligned, which would facilitate construction of the subcomponents from two-piece molds.
An artificial reef constructed from the deployment of a plurality of artificial reef modules for coral reef remediation in a close-packed array would result in a spatially complex habitat that provides a myriad of interstitial spaces well suited for sheltering the small reef fish important to sustaining a healthy, robust coral reef. The shaded lower surfaces of the upper, middle, and lower settling plates provide a protective microhabitat which is suitable to coral larvae seeking to settle and grow. Additionally, over time the individual artificial reef modules for coral reef remediation will slowly degrade and allow the tines to break off. This degradation closely approximates the fragmentation that occurs with natural branching coral.
Moderate wave action and water current will cause the primary and secondary tines of different artificial reef modules for coral reef remediation to become more interlocked than when initially deployed. However, increased motion due to the water may cause individual artificial reef modules for coral reef remediation to dislodge. Therefore, it may be necessary to include an anchor which would be inserted through a hole formed in the central body of the artificial reef module for coral reef remediation and anchored in the seabed.
The artificial reef module for coral reef remediation of the present invention overcomes the disadvantages of the prior art described above because it provides an artificial reef module which closely approximates a natural coral reef habitat in order to attract the proper marine life to facilitate the re-growth of damaged coral and to facilitate the growth of new coral. Moreover, artificial reef module for coral reef remediation of the present invention is made from non-polluting materials that will dissolve over time to minimize evidence of human intervention.
The dissolution of the artificial reef module for coral reef remediation of the present invention will allow it to break apart under wave action and moderate underwater currents. This will approximate the natural fragmentation of branching types of coral to aid in the dissemination of young corals and facilitate the reproduction of the coral. The artificial reef module for coral reef remediation may also be constructed from mass produced, prefabricated components to facilitate the deployment of the artificial reef modules in large numbers at low cost.
Finally, the artificial reef module for coral reef remediation provides an artificial reef module which, when deployed in plurality, creates an artificial reef structure with a natural, organic underwater appearance that is visually appealing to swimmers, snorkelers, and SCUBA divers.